1. Field of the Invention
The present invention relates to a method for determining whether a compound is an insulin receptor kinase activator.
2. Description of Related Art
The insulin receptor is present on virtually all cells and at high concentrations on the cells of the liver, skeletal muscles, and adipose tissue. Stimulation of the insulin receptor with insulin is an essential element in carbohydrate metabolism and storage.
Diabetic subjects either lack sufficient endogenous secretion of the insulin hormone (Type 1) or have an impaired insulin signaling to the glucose transport system and to glycogen synthase (Type 2). In Type 2 diabetics, major insulin-responsive tissues such as liver, skeletal muscle and adipose tissue exhibit the insulin resistance (Haring and Mehnert (1993), Diabetologia 36: 176-182; Haring et al. (1994), Diabetologia, 37 Suppl. 2: S149-S154).
Insulin receptor kinase activators stimulate autophosphorylation of the insulin receptor and stimulate the uptake of glucose into cells. Without intending to be bound by any theory, it is believed that insulin receptor kinase activators act directly on the kinase function of the receptor and do not necessarily compete with insulin for binding at the insulin-binding site, nor do they effect activation of the receptor by a mechanism similar to that exhibited by insulin.
Thus, insulin receptor kinase activators are directly able to activate the kinase to autophosphorylate, to potentiate the effects of insulin, to activate the kinase function of the receptor in phosphorylating insulin receptor substrate-1 (IRS-1) and to effect the increased uptake of glucose by adipocytes and insulin receptor-bearing cells in general and to lower blood glucose in diabetic subjects.
Additionally, insulin receptor kinase activators may be used to stimulate the kinase activity of an insulin receptor, to enhance the activation of the insulin receptor by insulin, to enhance the stimulation by insulin of cellular glucose uptake, and to stimulate the uptake of glucose in subjects who have diabetes, ketoacidosis, insulin resistance, hyperglycemia, lipodystrophy, or hypertriglyceridemia.
Insulin resistance is also found in many non-diabetic individuals, and may be an underlying etiologic factor in the development of the disease (Reaven (1988), Diabetes, 37: 1595-1607). For example, treatments for HIV infection have proven very effective in controlling the ravages of the terminal stage of the infection, AIDS, however, many of the drugs currently available have side-effects which induce insulin resistance.
Drugs currently used to suppress viral load and the resulting AIDS symptoms are called HIV protease inhibitors. Unfortunately, HIV protease inhibitors, which are required to maintain health in HIV-infected individuals, also carry the significant side-effect of inhibitor-induced insulin resistance leading to hyperglycemia that can progress to diabetes and ultimately life threatening ketoacidosis. (Carr et al. (1998), Lancet 351: 1881-1883; Carr et al. (1998), AIDS 12: F51-F58).
In addition to insulin resistance, other related disturbances in metabolism, such as lipodystrophy and hypertriglyceridemia, are also observed in HIV protease inhibitor treated patients (Roth et al. (1998), Clin Infect Dis 27: 65-67; Safrin et al. (1999), AIDS 13: 2493-2505; Carr et al. (1999), Lancet 353: 2093-2099; Behrens et al. (1999), AIDS 13: F63-F70). This complex metabolic side-effect profile of these very important drugs has all the hallmark features of the insulin-resistant state referred to as Syndrome-X (Reaven (1993), Annu Rev Med 44: 121-131).
For some patients, these metabolic side-effects greatly limit the use of these life-sustaining drugs. This side-effect profile was not recognized early in the development of these drugs, but once these inhibitors entered general clinical use, this problematic side-effect manifested itself in a large percentage of the treated population. The problem appears to be a class effect in that all the currently available HIV protease inhibitor drugs demonstrate this severe effect.
The molecular origin of this phenomena was recently identified in 3T3 L1 adipocytes (Murata et al. (2000), J Biol Chem 275(27): 20251-20254). The report provided evidence that at least three of the commercialized HIV protease inhibitor drugs also inhibit the glucose transporter from localizing to the cell membrane with the subsequent inhibition of glucose uptake by these cells. This inhibition of cellular glucose transport into cells by these HIV protease inhibitors is consistent with the elevation of glucose and lipids observed in the clinic for some patients being treated with these protease inhibitor drugs.
In the parent application, applicants disclosed that insulin receptor kinase activators reverse the HIV protease inhibitor side effect of metabolic disorders and can reverse the effects of insulin resistance the glucose uptake inhibition so caused. Such compounds are useful in treating HIV protease inhibitor induced insulin resistance, hyperglycemia, diabetes, ketoacidosis, lipodystrophy, and hypertriglyceridemia.
The disclosures of all documents referred to in this application are incorporated herein by reference.
This invention is a method of determining whether a compound is an insulin receptor kinase activator, comprising: administering the compound to a non-human mammal concurrently treated with an HIV protease inhibitor, administering glucose to the mammal, and measuring the level of plasma insulin or plasma glucose in the mammal, where a reduced level of plasma insulin or plasma glucose in the mammal compared to a comparable mammal that has been treated with the HIV protease inhibitor and administered the glucose, but not administered the compound, indicates that the compound is an insulin receptor kinase activator.
In a preferred embodiment, the HIV protease inhibitor is amprenavir, atazanavir, droxinavir, indinavir, lopinavir, nelfinavir, ritonavir, or saquinavir, or a pharmaceutically acceptable salt thereof; especially indinavir as the sulfate salt.
In a preferred embodiment, the mammal is a rat.